Mechanism of activation of renal Na+-K+-ATPase in the rat: effects of potassium loading.
Mechanism of activation of renal Na+-K+-ATPase in the rat: effects of potassium loading.
复制标题
大鼠肾 Na -K -ATP 酶激活机制：钾负荷的影响。
作者：
H. Rodriguez;W. C. Hogan;R. Hellman;S. Klahr
已在大鼠肾脏中研究了慢性钾负荷后 Na+-K+-ATP 酶的激活机制。钾负荷刺激肾脏皮质和髓质中Na+-K+-ATP酶的比活性。这种效应并不伴随细胞内RNA和蛋白质含量的普遍增加，并且不能用钾负荷对肾脏生长的影响来解释。酶诱导似乎不是由糖皮质激素或甲状腺激素内源水平的变化介导的。从 Na+-K+-ATPase 酶促反应的部分反应（Pi 中间体、哇巴因敏感 pNPPase）研究中获得的证据与大鼠慢性钾负荷增加肾皮质中酶单位（Na+泵）数量的解释一致。酶促反应的动力学参数（Km、K1/2、Vmax、Hill 系数）分析表明 K+ 负载对受刺激转运酶的动力学特性（亲和力、协同性）影响很小或没有影响。
The mechanism of activation of Na+-K+-ATPase after chronic potassium loading has been investigated in the rat kidney. Potassium loading stimulated the specific activity of Na+-K+-ATPase in the cortex and medulla of the kidney. This effect was not accompanied by a generalized increase in the cellular contents of RNA and proteins and could not be accounted for by an effect of potassium loading on renal growth. Enzyme induction does not appear to be mediated by changes in the endogenous levels of glucocorticoid or thyroid hormones. Evidence obtained from investigation of the partial reactions (Pi intermediate, ouabain-sensitive pNPPase) of the Na+-K+-ATPase enzymatic reaction is consistent with the interpretation that chronic potassium loading in the rat increases the number of enzyme units (Na+ pumps) in the cortex of the kidney. Analysis of the kinetic parameters (Km, K1/2, Vmax, Hill coefficients) of the enzymatic reaction indicates that K+ loading has little or no effect on the kinetic properties (affinity, cooperativity) of the stimulated transport enzyme.